A general synthetic strategy for ordered, extra-large mesoporous metal oxidesvia uniform sol–gel coating

Abstract

Mesoporous non-silicate oxides (MNSOs), with well-defined organization on the 2–50 nm size scale, may play a pivotal role in advancing vital disciplines such as catalysis, energy conversion and biotechnology. The vast majority of known MNSOs have a pore size less than 16 nm due to the limited dimensions of the organic templates. Herein, we present a simple and general method for the synthesis of MNSOs with extra-large three-dimensional mesoporous structures, which is based on uniform coating of non-silicate oxide nanoparticle precursors onto the surface of mesoporous silica EP-FDU-12. The successful synthesis of MNSOs relies on two key factors: the extra-large, 3-D open mesoporous networks of the EP-FDU-12 hard-template and the stable NSO nanoparticles formed in AcHE solution. Extra-large pore size and window size are prerequisites to avoid the local aggregation and phase separation of the coating metal oxides. The coating thickness can be easily controlled by changing the initial concentration ratio of raw materials. The successful uniform coating of NSOs in the AcHE sol–gel system allows us to synthesize a large variety of EP-NSOs (EP-Al₂O₃, EP-TiO₂, EP-ZrO₂, EP-Ce–TiO₂ and EP-K–Ce–TiO₂). The EP-Al₂O₃ and Pd/EP-Al₂O₃ catalysts have been investigated in the F–C alkylation and n-hexane combustion reactions, which serve as two examples to show that catalytic reactions can benefit from the extra-large, 3-D open mesoporous networks with improved adsorption and diffusion of reactants and designed metal-to-support interfaces.